•GO and Ni2+ were reduced simultaneously during the reduction process.•The Ni/RGO nanocomposites exhibits enhanced EM absorption performance.•The impedance matching and interfacial polarization could be obtained.•This work provides a typical sample with enhanced electromagnetism.In this work, Ni/reduced graphene oxide (RGO) nanocomposites were prepared via an in-situ reduction step. During the reduction process, graphene oxide (GO) and Ni2+ ions were reduced simultaneously and consequently, the magnetic Ni nanoparticles were dispersed in nonmagnetic RGO matrix homogeneously. Combining the cooperative effect from RGO and Ni, the as-fabricated Ni/RGO composites exhibit enhanced EM absorption performance as compared to the individual compositions due to the improvement of the electromagnetic loss performance and the enhanced electromagnetic impedance matching.

In the current work, we synthesized Ni/C composites from Ni/cellulose composites and analyzed how well the products absorbed microwaves. The Ni/C composite products showed a maximal reflection loss (RL) of −53.8 dB at 4.72 GHz with a sample thickness of 4.5 mm, and the RL values exceeded −10 dB covers almost the whole tested frequency ranges (2–18 GHz). These results were attributed to a combination of the magnetic loss and the dielectric loss. This work is expected to contribute to the development of materials that absorb a broad region of the electromagnetic wave and to the recycling of cellulose.